Armature for electromagnetic device

ABSTRACT

AN ARMATURE FOR AN ELECTROMAGNETIC DEVICE INCLUDING ELECTROMAGNETIC-FIELD PRODUCING MEANS AND ARMATURE OPERATIVE BY THE MEANS, THE ARMATURE INCLUDES A MANDREL HAVING A WEB WITH THICKENED END PORTIONS AND HAVING AN ELONGATED THIN METAL STRIP WRAPPED AROUND THE WEB IN SUCCESSIVE CONVOLUTIONS WITH THE EDGES OF THE STRIP BEING IN CONTACT WITH THE CORRESPONDING END PORTIONS.

United States Patent [72) inventor Richard H. Buckwalter [56] References Cited M A l N gsfggg UNITED STATES PATENTS 1 P 3.050,663 8/1962 Zipper. 335/251 [22] Filed N0v.18 1969 [45] Patented June28 1971 3.196.322 7/l965 Harper U 335/251 3517,35) 6/1970 Trbovich etal 335/279X [73] Asslgnee Westinghouse Electric Corporation Pittsburgh, Pa.

[54] ARMATURE FOR ELECTROMAGNETIC DEVICE Primary Examiner-G Harris AttorneysF. Shapoe and Lee P. Johns convolutions with the edges of the strip being in contact with the corresponding end portions.

Patentea 'June 28, 1971 3 Sheets-Sheet 1 INVENTOR Richard H. B kwolrer ATTORNEY Patented June 28, 1971 3,588,769

3 Sheets-Sheet 2 Patentd June 28, 1911 3 Sheets-Sheet l 92 FIG. l2

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an armature and, more particularly, it pertains to a mandrel structure and windings thereon.

2. Description of the Prior Art Armatures for electromagnetic devices are provided in various forms. For example, armatures for torque motors which move through a relatively short distance in response to an electromagnetic field are useful for a multitude of purposes including the operation of control valve switches, relays, and the like. Such armatures are particularly useful where reliability and fast response are necessary. Armatures of various construction have been used depending upon their particular application. A conventional-type of armature composed of thin laminations of soft magnetic material which are stacked and adhesively bonded together have proven unsatisfactory where rapid motion of the armature is necessary because shock levels in excess of the mechanical strength of the lamination stackmay occur. In addition, the bonding and assembly of laminae stacks is difficult even under ideal manufacturing conditions. Attempt to overcome some of the difficulty by providing a peripheral reinforcement strap around the laminated stack so as to achieve the additional advantage of reliability resulted in a low yield without reduction in manufacturing costs.

SUMMARY OF THE INVENTION It has been found in accordance with this invention that the foregoing problems may be overcome by providing an armature composed of a mandrel on which a winding of thin soft magnetic metal strip is wrapped; the mandrel being composed of an intermediate web portion between enlarged end portions; the winding is wrapped around the web portion and having its opposite edges preferably in contact with the adjacent edges of the corresponding enlarged end portions of the mandrel; the assembly of the mandrel and wrapped metal strip is suitable for pivotal mounting between two spaced pairs of pole pieces of electromagnetic field-producing means.

Accordingly, it is a general object of this invention to provide an armature which is adapted to simple construction techniques and is mechanically reliable.

It is another object of this invention to provide an armature which eliminates the limitations of stacked laminae constructions and provides good magnetic operating characteristics.

Finally, it is an object of this invention to satisfy the foregoing objects and desiderata in an expedient manner.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of the nature and objects of this invention reference is made to the drawings, in which:

FIG. 1 is a partial diagrammatic perspective view, partially in section, or a torque motor;

FIG. 2 is a vertical sectional view through the motor of FIG. 1 taken on the line II-Il of FIG. I;

FIG. 3 is a fragmentary perspective view;

FIG. 4 is a sectional view taken on the line IV-IV of FIG. 2;

FIG. 5 is a vertical sectional view of another embodiment of the armature;

FIG. 6 is a sectional view taken on the line VI-VI of FIG. 5;

FIGS. 7 and 8 are views of other embodiments of the armature construction;

FIG. 9 is a plan view of a prior art armature;

FIG. 10 is a vertical sectional view taken on the line I010 of FIG. 9;

FIG. 11 is a vertical sectional view of another embodiment of the invention;

FIG. 12 is a vertical sectional view taken on the line XII-XII ofFIG. I1; and

FIG. 13 is a vertical sectional view of another embodiment ofa solenoid plunger.

Similar numerals refer to similar parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, torque motor is generally indicated at 10. It includes a pair of spaced permanent magnets 12 and 14, and an armature 16 disposed therebetween. The armature 16 has opposite end portions one of which is disposed between pairs of poles pieces 18 and 20 of the magnet 12, while the other end portion of the armature 16 is disposed between pole pieces 22and 24 of the magnet 14. T he torque motor 10 also includes a pair of shunt members 26 and 28, the former of which is attached to and extends between the pole pieces 18 and 22 and the latter of which is attached to and extends between the pole pieces 20 and 24.

The armature I6 is mounted for pivotal movement on a cylindrical yoke 30 disposed centrally between the magnets 12 and 14. The yoke 30 is of cylindrical shape and is provided with a slot to enable the armature 16 to be slid onto it. The yoke has an integral pair of armature mounting members 32 and 34 which are axially aligned with each other and with the yoke. The outer end of each mounting member 32 and 34 includes a flange 36 and 38, respectively, which are attached by suitable means such as screws 40 to the side walls 42 and 44 of a casing enclosing the torque motor 10. The torsional mounting members 32 and 34 are torsion means which enable resilient rotary movement of the armature 16 out of the neutral or centrally disposed position in the space between pole pieces 18-20 and 2224 as shown in FIGS. 1 and 2. When a current is applied to a control winding 46 extending around the armature, the armature 16 rotates either clockwise or counterclockwise depending on the polarity of the current applied to the winding and stresses the torsional mounting means 32 and 34. As soon as the current flow is terminated the mounting members 32 and 34 return the armature 16 to the neutral position. 4

As shown in FIGS. 1 and 2 a pair of elongated rods 48 and 50 are attached to the end portions of the armature 16 in a suitable manner such as by threaded engagement with screw threads in apertures in the armature. The rods 48 and 50 perform a function such as actuating a valve, switch, relay, or other suitable device which may be activated or inactivated by the movement of the armature 16.

The magnets 12 and 14 are preferably permanent magnets that provide the corresponding pole pieces 1824 with a magnetic flux of the appropriate polarity. The pole pieces are composed of any suitable soft magnetic metal such as iron. Each pole piece I824 has a notch 50 to provide a space to accommodate the rods 48 and 50. The shunt members 26 and 28 are composed of suitable soft magnetic material such as an alloy composed of 50 percent iron and 50 percent cobalt.

As shown in FIG. 2 the armature 16 is composed of a mandrel 54 and turns or windings 56 or soft magnetic strip. The mandrel 54 includes an intermediate web 58 between a pair of end portions 60 and 62. The end portions 60 and 62 are preferably integral with the intermediate web portion 58 and are enlarged or have steps 64 and 66 where the end portions and web are joined. As shown in FIG. 3, the step 66, which is typical of both steps 64 and 66, includes similar upper and lower surfaces or shoulders 68 which extend horizontally from an edge surface 70 of the end portion 62. The step 66 likewise includes an edge surface 72 as well as similar opposite end surfaces 74. As will be observed in FIG. 3 the web is narrower than the end portions 62 and 64, as well as step 66.

Another embodiment of the mandrel, as shown in FIGS. 5 and 6, has a web 59 which extends between and joins opposite end portions 61 and 63 having similar edge surfaces 78. This embodiment of the mandrel hasa single step instead of the two steps 64 and 66 of the mandrel construction of FIGS. 2 and 3. In both embodiments of FIGS. 2 and 5, a first elongated strip of suitable soft magnetic material of a width equal to the space between edge surfaces 72 is wound around the web to form a continuous wrapping of successive convolutions or turns with the outermost convolution ll'l alignment with the upper and lower shoulders 68 of the end portions 60 and 62. then a wider strip of magnetic strip is wound between edge surfaces 70 until a wrapping 56 up to the level of the outer surfaces of62 and 64 is applied As shown in FIG. 2 the armature 16 including the mandrel 54 and turns 56 is inserted into an opening 78 in the yoke 30 where it is held by suitable means horizontally in place in neutral position. Similar tapped holes 80 are provided in each end portion 60 and 62 for engagement with threaded portions 82 of the rods 48 and 50. When a direct current is applied to the coil 46, the armature moves clockwise or counterclockwise (in the direction of the arrows 84) depending upon the polarity ofthe current. thereby moving the rods 48 and 50.

The material of the turns 56 as well as the mandrel 54 is composed of any soft magnetic material with a minimum saturation of 16 kilogauss and having a coercive force of up to one oersted. A typical alloy of which the mandrel 54 and winding 56 may be composed is an alloy containing 50 percent cobalt, 48 percent iron, 2 vanadium, and traces of incidental impurities and having a high maximum flux density. Another material of which the mandrel and turns may be composed is an alloy containing 50 percent iron and 50 percent cobalt. Before wrapping the winding 46 around the web 58 of the strip of winding is preferably coated with an insulating material such as magnesium methylate [Mg(CI-I Other suitable insulatthe end portions 60 and 62, whereby the magnetic reluctance is reduced even more than by the embodiment shown in FIGS. 2 and 3 Another embodiment is shown 111 FIG. 8 in which the steps 71, 73, and 75 of FIG. 7 are replaced by inclined surfaces 77 and 79 are provided between the end portions 60 and 62 and the web 58, whereby the effect of an infinite number of steps and their resulting reduction of magnetic reluctance is obtained.

The following example is illustrative of the present invention.

EXAMPLE Mandrels of each type shown in FIGS. 2 and 5, was made having a web thickness of 0.035 inch. Each mandrel had overall dimensions of 1.685 inches by 0.715 inch by 0.200 inch. The length of the web without any step (FIG. was 0.900 inch while the length of the web with the step construction of FIG. 3, at each end was 0.800 inch with the width of each shoulder being 0.05 inch. The strip of the magnetic winding wrapped around the web was 0.200 inch thick and was composed of an alloy containing 50 percent iron, 48 percent cobalt, and about 2 percent vanadium. When a direct current of about 1.5 amperes was applied to the field coil 46 in each model, a force of 8 /2 lbs. was exerted on the rods 48 and 50 attached to the end of the armature. The test results of such models are shown in the Table.

1 1. 46 amperes maximum D.C. to obtain a 8.5 lbs. pull. I 9 1.80 milliseconds maximum for armature closure for 0.024 inch travel under capacitor discharge.

ing materials for coating this strip are phosphates and magnesium oxide.

Prior to winding the strip is annealed for softness and to enable a snug fit and good packing during wrapping on the web. For that purpose, it is desirable that the width of the strip be substantially equal to the distance between the edge surfaces 70 and 72 (FIG. 2), or surfaces 78 (FIG. 5). The preferred thickness of the winding strip is 2 mils. whereby to convolutions of the winding may be applied on the web 58 for a mandrel 0.200 inch thick and 0.715 inch wide, wherein the web is 0.035 inch thick and 0.549 inch web. In this case the web length was 0.800 inch between edge surfaces 72, and 0.900 inch between edge surfaces 70 of the end portions 62 and 64.

For most efficient results it is necessary that the edges of the windings be in close abutment with edge surfaces 70 or 78. Where a substantial clearance or gap exists between the edges of the winding 56 and the edge surfaces of the end portions 60 and 62, the flux density flowing between the windings and the end portions is reduced.

The preferred mandrel embodiment is that of the FIG. 2, having the two steps 64 and 66. The steps 64 and 66 comprise the shoulders 68 and 74 (FIG. 3) to avoid a gap between the outer laps or convolution of the windings and the end portions, and thereby minimize the loss of flux density which would otherwise occur. By providing the steps 64 and 66 at each end ofthe web portion 58 of the magnetic reluctance is reduced and less energy is required to operate the armature. The beneficial effect of the steps, however, is substantially lost when they exceed a length or about 10 percent of the overall length of the web portion 58.

Another embodiment is shown in FIG. 7 in which a plurality of steps 71, 73, and 75 are provided between the web 58 and With regard to the test results of the Table, the specifications required 1.46 maximum amperes for the static test and 1.8 maximum milliseconds for the ends of the armature to move 0.024 inch of travel for the dynamic test. The static test is a measure of direct current required in the excitation coil 46 to deflect the pole face of the armature through 0.015 inch from neutral position pulling against a spring and a weight of 8.5 lbs. and assisted by the permanent magnetic previously adjusted to produce about 0.021 inch deflection on an armature in the absence of the 8.5 lb. weight. The dynamic test is a measure of time required for the armature to move through the prescribed distance under capacitance discharge excitation.

Model No. 0 was an armature of prior art stacked core construction as shown in FIGS. 9 and 10. It included a plurality of laminations 86 secured together by a bonding agent comprising an epoxy resin. A tapped rivet 88 was disposed in an opening at each end of the armature and brazed in place. A metal strip 90 was wrapped around the assembly to hold the laminated strips 86 and rivets in tact. Test results of Model No. 0 indicated static and dynamic values of 1.20 amps. and 1.6 milliseconds, respectively, which were well within the specification limits. But the armature was regarded as impractical because of the difficulty of assembly during its manufacture.

Armature No. 5A, having the structure shown in FIG. 4 (with no step between the end portions 60 and 62 and the web 56 having a total weight of 31.75 grams required only 1.19 amperes to develop 8.5 lbs. of pull, which was well below the specification maximum of 1.46 amperes; however, the armature required 1.89 milliseconds to move the required distance which was above the maximum time limit of 1.8 milliseconds. A slight reduction in the weight of the armature such as by using a shorter length of wrapping 56 would satisfy the dynamic test without exceeding the static test limits.

Armature Model No. hanng the stepped construction performed most SZlIlSfaClOIll) under the combined test conditions with a total pulse of 1.41 amps under the static test and a total of 166 milliseconds under the dynamic test.

Armature Model No 8 having a single stepped construc tion of FIG. 2 was purposely made llh about I gram less in weight (as compared with Model No 7). by using a shorter strip 56. As a result the armature required slightly more current (1.54 amperes) fit still within specification and it did move the required distance in 1.61 milliseconds. The reason for the excess current was due to the reduced amount of magnetic strip material which failed to support sufficient flux to attain the static test magnetization requirement. In summary armature Model Nos. 7 and 8 were attempts to optimize the static and dynamic tests and it was found that the static test values go up as the dynamic test values go down and vice versa.

Other embodiments of the invention are useful in one type of high speed magnet 92 as shown in FIGS. 11 and 12. The magnet 92 inclucles a core 94, a coil 96, and a solenoid-type plunger 98. The core 94 is constructed ofa plurality oflaminations 100 of suitable material such as highly permeable soft iron which laminations are clamped together in a conventional manner such as between brass plates 102 by spaced rivets 104. The core 94 has a generally C-shape and includes spaced guide portions 106 facing surfaces 108 and 110 forming an opening in which the plunger 98 is reciprocably operative as indicated by an arrow 112. Thus, the plunger 98 is movable between the solid line position and a broken line position 113 as shown in FIG. 11. When the coil 96 is energized. the plunger 98 is pulled into the coil (position 113) whereby an associated mechanism 114 (attached to the plunger) is operated. Upon deenergizing the coil 96, the plunger 98 is returned to the solid line p sition (FIG. 11) by suitable means such as a spring (not shown).

Prior constructions of the plunger included laminations which were secured together in a suitable manner such as the armature shown in FIGS. 9 and 10. In accordance with this invention the plunger 98 has a construction substantially similar to that of the armature 16. Thus the plunger 98 includes a mandrel having a pair of end portions 116 and 118 (FIG. 11) and an integral connector 120 (FIGS. 11 and 12). The mandrel also includes a winding 122 (similar to the winding 58) which is wrapped around the connector 120 as shown in FIG. 12. In order to fit between the guide portions 106 the connector 120 and windings 122 have a rectangular cross section. However, where the opening between the guide portions 106 is of a different shape, such as circular, a roimd mandrel 123 (FIGv 13. is provided having a round connector 124 and windings I26 wrapped thereon The unique armature and mandrel construction of the foregoing embodiments may be adapted for use in a wide range of electromagnetic devices such as high speed torque motors. high speed closing magnets, and AC electromagnets of all types In general, any magnetic device requiring laminated construction for speedup response or reduction of operating temperatures where stack construction geometry can be achieved by torroidal winding onto a machined mandrel, whereby manufacturing assembly is simplified and/or mechanical reliability in service is increased.

Although the best known embodiments of the invention have been described in detail. it is understood that the invention is not limited thereto or thereby.

Iclaim:

1. An electromagnetically responsive element comprising a mandrel of soft magnetic material having enlarged end portions and a web therebetween, and a winding comprising at least one elongated metal strip of soft magnetic material wrapped around the web in successive convolutions with the edges of the strip being adjacent to and substantially abutting corresponding enlarged end portions.

2. The apparatus of claim 1 wherein each end portion of the mandrel includes at least one stepped portion.

3. The apparatus of claim 2 wherein the depth of each stepped portion is no greater than 10 percent of the length of the web.

4. The apparatus of claim 1 wherein the soft magnetic material of the mandrel and winding has aminimum saturation of 16 kilogauss.

5. In a torque motor having two spaced magnets each with a pair of pole pieces, an armature centrally pivotally mounted between the magnets and with one end portion between one pair of pole pieces and with another end portion between another pair of pole pieces, torsion means for holding the end portions of the armature in a neutral position between the pole pieces, a rod carried by the armature and movable therewith, the improvement wherein the armature comprises a mandrel and windings, the mandrel having enlarged end portions and a web therebetween the winding comprising at least one elongated metal strip wrapped around the web in successive convolutions with the edges of the strip being adjacent to the corresponding enlarged end portions, and the mandrel and winding being composed of soft magnetic material.

6. The apparatus of claim 5 wherein each end portion of the mandrel includes at least one stepped portion.

7. The apparatus of claim 5 wherein the metal strip has an insulation coating of Mg(CI-I; 

